<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    var maximumGap = function (nums, maxNum = 0) {
      if (nums.length < 2) return 0
      nums.sort((a, b) => a - b).reduce((pre, val) => ((val - pre) > maxNum && (maxNum = (val - pre)), val))
      return maxNum
    };
    console.log(maximumGap([3, 6, 9, 1]))
  </script>
</body>

</html>